As an example of a seat apparatus for a vehicle including a double seat (a seat including two seating positions for accommodating two occupants) and a single seat (a seat including one seating position for accommodating one occupant) which adjoin each other in a width direction of the vehicle, a seat apparatus disclosed in DE103 11 869A1 (hereinafter, referred to as reference 1) has been known. According to the reference 1, the double seat is structured so that a three-point supporting seatbelt is assembled thereon for each seating position. Accordingly, a shoulder belt guide member (through anchor) for guiding a shoulder belt and a belt anchor of the three-point supporting seatbelt are provided at an approximately intermediate portion of the double seat in the width direction (lateral direction) of the vehicle. Further, seat slide mechanisms for adjusting a position in a front-rear direction of the vehicle is provided at lateral sides of the double seat, respectively. Still further, a seatback reclining mechanism (recliner) for adjusting a reclining angle of a seatback and an auxiliary seat slide mechanism which is movable in the front-rear direction of the vehicle are provided at the laterally intermediate portion of the double seat, at which the belt anchor and the shoulder belt guide member are also provided. The auxiliary seat slide mechanism functions as a reinforcement member and receives a separating load and a bending moment, i.e., a load generated by the shoulder belt anchor provided at the laterally intermediate portion of the double seat and a load generated by the lap belt anchor provided at the laterally intermediate portion of the double seat, when a collision of the vehicle occurs, for example. Thus, the seat is suppressed from separating from a vehicle floor.
A double seat including such structure is also disclosed in JP 2002-337576A and in JP2002-347497A, as an example.
According to the reference 1, the double seat includes three seat slide mechanisms (the seat slide mechanisms disposed at the lateral sides of the double seat and the auxiliary seat slide mechanism), which extend in the front-rear direction of the vehicle while having a distance from each other in the lateral direction. Accordingly, the weight of the seat apparatus is increased, and also the structure of the seat apparatus becomes complicated. Further, because the three seat slide mechanisms occupy a floor space defined at a back side of the double seat, i.e., a foot space of an occupant seated on a backside seat disposed at a backside of the double seat, a seating attitude of the occupant seated on the backside seat may be restrained.
A need thus exists for a seat apparatus for a vehicle, which is not susceptible to the drawback mentioned above.